I also have a JRT
He's a happy, friendly little dog, likes to say hello to people and likes a lot of fuss.
Some dogs he will say hello to, mostly rolls over for them, some he ignores. Mostly will play happily.
Generally he is wary of cats!
Loves to chase balls, disembowel squeaky toys and play tug.
I only let him off lead if we are out in country or on beach as he has no sense at all regarding traffic, always pulling on his lead to run out in road. Recall - he will come for a treat as part of training at home, out he will return with his ball and stay within 2 feet of you but is difficult getting back on his lead.
Not at all snappy, quite cuddly, curls up on my lap. Doesn't like going out in rain.
As others have said, moults a lot. Will dig if left in garden and his 'demands ' for play are not met.
His main downside is his barking. He's very, very vocal. And his 'demand' bark is very high pitched. He barks if he's happy, excited, hungry, cross. He also guards us from any noise across the street, or on TV and will suddenly awake, growl then bark, bark, bark!
He's a very beautiful little dog. 